maybe MIT, you can use it freely for any project you're working on.
I am bad in licenses but it seems to me it conflicts with what you wrote on the page (It looks like more CC0 because IIRC MIT says that "credits" are necessary)... And MIT is good for code but not for assets... Usually people use CC licenses. If it is really MIT, so please, point it on the page. Itch allows you to add license to the metadata of the page "Edit asset pack->Metadata->Release Info->License for assets" but only if it is CC license...
You can leave a comment here to support my proposal about making metadata visible for those who are interested in it https://itch.io/t/2919128/metadata-encouragement#post-7952450